<p>The purpose of this thesis is to provide a detailed description of recent methods and scientific basis for characterizing earthquake sources within a certain region with distinct tectonic environments. The focus will be on those characteristics that are most significant to the ground-shaking hazard and on how we can incorporate our current knowledge into hazard analyses for engineering design purposes. I treat two particular geographical areas where I think current hazard analysis methods are in need of significant improvement, and suggest some approaches that have proven to be effective in past applications elsewhere. A combined hazard procedure is used to estimate seismicity in <i>northern Central America</i>, where there appear to be four tectonic environments for modeling the seismogenic sources and in <i>Iran</i>, where the large earthquakes usually occur on known faults. A preferred seismic hazard model for northern Central America and the western Caribbean plate based on earthquake catalogs, geodetic measurements, and geological information is presented. I used the widely practiced method of relating seismicity data to geological data to assess the various seismic hazard parameters and test parameter sensitivities. </p><p>The sensitivity and overall uncertainty in peak ground acceleration (PGA) estimates are calculated for northwestern Iran by using a <i>specific randomized blocks design</i>. A Monte Carlo approach is utilized to evaluate the ground motion hazard and its uncertainties in northern Central America. A set of new seismic hazard maps, exhibiting probabilistic values of peak ground acceleration (PGA) with 50%, 10%, and 5% probabilities of exceedance (PE) in 50 years, is presented for the area of relevance. <i>Disaggregation of seismic hazard</i> is carried out for cities of San Salvador and Guatemala by using a spatial distribution of epicenters around these sites to select design ground motion for seismic risk decisions. </p><p>In conclusion, consideration of the effect of parameters such as seismic moment, fault rupture, rupture directivity and stress drop are strongly recommended in estimating the near field ground motions. The rupture process of the 2002 Changureh earthquake (<i>M</i><i>w</i> = 6.5), Iran, was analyzed by using the<i> empirical Green’s function (EGF) method</i>. This method simulates strong ground motions for future large earthquakes at particular sites where no empirical data are available.</p>

A comprehensive study has been carried out to investigate the correlation between deformation demands of frame structures and a number of widely cited ground motion intensity parameters. Nonlinear response history analyses of single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) models derived from sixteen reinforced concrete frames were carried out under a set of eighty ground motion records. The frames were selected to portray features of typical low-to-mid rise reinforced concrete structures. The records contained in the ground motion database were compiled from the recorded ground motions with the intention to possess a broad range of amplitude, frequency content and duration characteristics that shift selected frames into various degrees of elastic as well as inelastic response. Maximum deformation demands of SDOF models and the maximum interstory drift ratios of MDOF models, response parameters of interest, were computed employing 1280 nonlinear response history analyses. Computed response parameters were compared with the ground motion intensity parameters employed and correlation between them were quantified through coefficients of correlation and determination. The results revealed that the spectral intensity parameters including spectral amplitudes over a range of period covering the frame structures have the strongest correlation and present better relationship with the deformation demands compared to the intensity parameters that are based on a single amplitude such as PGA, PGV and spectral acceleration. Besides analytical study, association of ground motion parameters with observed damage has been investigated and no clear trend has been observed between the performance of the buildings and the seismic indices.

Evaluation of the seismic stability of slopes often involves an estimate of the expected sliding displacements. This evaluation requires a suite of acceleration-time histories as input motions. The methods of selecting and scaling these motions can affect the computed sliding displacements. Linear scaling of recorded ground motions and modification of recorded motions by spectral matching are common approaches used for ground motion selection and these approaches were used in this study to select motions for use in sliding displacement analyses. Rigid sliding block analyses and decoupled flexible sliding block analyses were performed using a suite of linearly scaled motions and a suite of spectrally matched motions. . Generally, the spectrally matched motions predict 10 to 30%, on average, smaller displacements and significantly less variability than the linearly scaled motions, when both suites of input motions were developed to match the same acceleration response spectrum. When both suites of input motions were developed to match the same peak ground velocity and acceleration response spectrum, the spectrally matched motions generally predict 5 to 15%, on average, larger displacements than the linearly scaled motions. Because ground motion parameters beyond acceleration response spectrum affect the computed sliding displacement, parameters such as peak ground acceleration (PGA), peak ground velocity (PGV) and mean period (T[subscript m]) should be considered in selecting and scaling motions for use in sliding displacement analyses. / text

The seismic design maps on ASCE 7-05, International Building Code- 2006/2009, assumed uniform hazard ground motion with 2% probability of exceedance in 50 years for the entire conterminous U.S. But, Luco et al in 2007 pointed out that as uncertainties in collapse capacity exists in structures, an adjustment on uniform hazard ground motion was proposed to develop new seismic design maps. Thus, risk-targeted ground motion with 1% probability collapse in 50 years is adopted on ASCE 7-10. Even though these seismic design maps are developed for buildings, performance-based bridge design is done using same maps. Because significance difference lies on design procedure of buildings and bridges this thesis suggests some adjustment should be made on uncertainty in the collapse capacity(β) when using for bridge design. This research is done in 3 cities of U.S— San Francisco, New Madrid and New York. Hazard curve is drawn using 2008 version of USGS hazard maps and risk- targeted ground motion is calculated using equation given by Luco et al adjusting the uncertainty in collapse capacity(β) to be 0.9 for bridge design instead of 0.8 as used for buildings. The result is compared with existing result from ASCE 7-10, which uses β=0.6. The sample design response spectrum for site classes A, B, C and D is computed for all 3 cities using equations given in ASCE 7-10 for all β. The design response spectrum curves are analyzed to concluded that adjustment on uncertainty in collapse capacity should be done on ASCE 7-10 seismic design maps to be used for performance-based bridge design.

As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motionthe elastic response to winter accumulation and spring melt seasonswith peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1 sigma confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22757号 / 工博第4756号 / 新制||工||1744(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 五十嵐 晃, 教授 高橋 良和, 准教授 古川 愛子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The theoretical and experimental investigations presented in this thesis are primarily related to the dynamic response of inelastic multi-storey building frames subjected to strong ground motions. The main purpose is to investigate, both analytically and experimentally, those aspects of the dynamic response characteristics which are of importance in aseismic design. In the first part of the thesis, the various parameters pertaining to the structural system are varied in a systematic manner and an assessment is made of the influence of this variation on the maximum response characteristics of the dynamic system. The second part of the thesis consists of an experimental investigation into the inelastic dynamic response of multi-storey frames. The comparison of experimentally obtained inelastic response and that predicted theoretically indicated a good agreement between the two. / Thesis / Doctor of Philosophy (PhD)

This thesis focuses on two different topics in seismology: imaging the global structures of the mantle transition zone discontinuities and studying the site response effects in the Atlantic and Gulf Coastal Plain. Global structures of the mantle transition zone discontinuities provide important constraints on thermal structures and dynamic processes in the mid mantle. In this thesis, global topographic structures of the 410- and 660-km discontinuities are obtained from finite-frequency tomography of SS precursors. The finite-frequency sensitivities of SS waves and precursors are calculated based on a single-scattering (Born) approximation and can be used for data selection. The new global models show a number of smaller-scale features that were absent in back-projection models. Good correlation between the mantle transition zone thickness and wave speed variations suggests dominantly thermal origins for the lateral variations in the transition zone. The high-resolution global models of the 410- and 660-km discontinuities in this thesis show strong positive correlation beneath western North America and eastern Asia subduction zones with both discontinuities occurring at greater depths. Wavespeed and anisotropy models support vertical variations in thermal structure in the mid mantle, suggesting return flows from the lower mantle occur predominantly in the vicinity of stagnant slabs and the region overlying the stagnant slabs. In oceanic regions, the two discontinuities show a weak anti-correlation, indicating the existence of a secondary global far-field return flow. The Atlantic and Gulf Coastal Plain is covered by extensive Cretaceous and Cenozoic marine sediments. In this thesis, the site response effects of sediments in the Coastal Plain region relative to the reference condition outside that region are investigated using Lg and coda spectral ratios. The high-frequency attenuation factors (kappa) in the Coastal Plain are strongly correlated with the sediment thickness. At frequencies between 0.1-2.86 Hz, the Lg spectral ratio amplitudes are modeled as functions of frequency and thickness of the sediments in the Coastal Plain. Analysis of the residuals from the stochastic ground motion prediction method suggests that incorporating the site response effects as functions of sediment thickness may improve ground motion prediction models for the Coastal Plain region. / Doctor of Philosophy / The mantle transition zone is the region in the Earth’s interior between depths of ∼410 km and ∼660 km. The structure of the mantle transition zone plays an important role in understanding temperature variations and mass exchanges in the interior of the Earth. This dissertation aims at resolving depth variations of the top and bottom boundaries of the mantle transition zone at a global scale using underside reflected seismic waves. The advanced method used here resolved stronger small-scale depth variations of the boundaries than a conventional method using the same dataset. The two mantle transition zone boundaries both occur at depths greater than the global average beneath eastern Asia and western North America where cold oceanic lithosphere subducted under the continents. This positively correlated behaviors of the two boundaries agree with a scenario where cold subducted slabs have been horizontally deflected and stagnant above the bottom boundary of the mantle transition zone while hot materials beneath the mantle transition zone flow upwards due to the stagnant slabs penetrating the bottom boundary of the mantle transition zone. This dissertation also provides an examination of the differences between response of earthquake ground shaking in the Atlantic and Gulf Coastal Plain and that outside the Coastal Plain using seismic-wave spectral ratios. Ground shaking in the Coastal Plain is found to be amplified at low frequencies and de-amplified at high frequencies relative to that outside the Coastal Plain due to the extensive marine sediments in the Coastal Plain region. The amplification and attenuation factors can be estimated from spectral ratios and are found to be strongly correlated with the sediment thickness in the Coastal Plain. The spectral ratio functions derived in this dissertation may be adopted by studies on analyzing the seismic hazard in the Central and Eastern United States.

Ground motions from earthquakes are known to be affected by earth's surface topography. Topographic effects are a result of several physical phenomena such as the focusing or defocusing of seismic waves reflected from a topographic feature and the interference between direct and diffracted seismic waves. This typically causes an amplification of ground motion on convex features such as hills and ridges and a de-amplification on concave features such as valleys and canyons. Topographic effects are known to be frequency dependent and the spectral accelerations can sometimes reach high values causing significant damages to the structures located on the feature. Topographically correlated damage pattern have been observed in several earthquakes and topographic amplifications have also been observed in several recorded ground motions. This phenomenon has also been extensively studied through numerical analyses. Even though different studies agree on the nature of topographic effects, quantifying these effects have been challenging. The current literature has no consensus on how to predict topographic effects at a site. With population centers growing around regions of high seismicity and prominent topographic relief, such as California, and Japan, the quantitative estimation of the effects have become very important. In this dissertation, we address this shortcoming by developing empirical models that predict topographic effects at a site. These models are developed through an extensive empirical study of recorded ground motions from two large strong-motion datasets namely the California small to medium magnitude earthquake dataset and the global NGA-West2 datasets, and propose topographic modification factors that quantify expected amplification or deamplification at a site. To develop these models, we required a parameterization of topography. We developed two types of topographic parameters at each recording stations. The first type of parameter is developed using the elevation data around the stations, and comprise of parameters such as smoothed slope, smoothed curvature, and relative elevation. The second type of parameter is developed using a series of simplistic 2D numerical analysis. These numerical analyses compute an estimate of expected 2D topographic amplification of a simple wave at a site in several different directions. These 2D amplifications are used to develop a family of parameters at each site. We study the trends in the ground motion model residuals with respect to these topographic parameters to determine if the parameters can capture topographic effects in the recorded data. We use statistical tests to determine if the trends are significant, and perform mixed effects regression on the residuals to develop functional forms that can be used to predict topographic effect at a site. Finally, we compare the two types of parameters, and their topographic predictive power. / Ph. D.

Seismic hazard calculations for sites in eastern North America have traditionally assumed a Poisson process to describe the temporal behavior of earthquakes and have employed the Gutenberg-Richter relationship to define the frequency distribution of earthquake magnitude. For sites in areas where geological information indicates recurrent, large earthquakes, however, such data imply a rate for large events which often exceeds that predicted by the Gutenberg-Richter relationship. One way in which this discrepancy can be reconciled is to assume that the larger events occur as a time-dependent, or renewal, process and possess a "characteristic earthquake" magnitude distribution. The main purpose of this study is to make a quantitative comparison of seismic hazard estimates for Charleston of the influences of 1) the Poisson temporal model assuming the Gutenberg-Richter and characteristic earthquake magnitude recurrence relationships with 2) the renewal temporal model assuming the characteristic magnitude recurrence relationship. Other issues that are examined are the sensitivity of uncertainties of hazard model parameters such as maximum magnitude and seismic source delineation. Probabilistic seismic hazard calculations for the next 50 years were performed at Charleston for all potential seismic sources. The highest estimate of seismic hazard was obtained with the Poisson temporal model and characteristic earthquake recurrence relationship. The lowest hazard was obtained with the renewal temporal model and characteristic magnitude recurrence relationship. The results of this study are in good agreement with hazard estimates for Charleston in the most recent national seismic hazard maps. / Master of Science